---
title: "Radon Glossary: Plain-Language Terms, Units and Systems"
url: https://vermontradon.com/radon-glossary/
description: "Radon terms in plain words: action level, pCi/L, Bq/m³, ASD, HRV, aeration, long-term and short-term tests, NRPP and NRSB, and more, each with its source."
last_reviewed: 2026-10-17
source: "Vermont Department of Health; U.S. EPA; Health Canada; CRCPD. Each fact is footnoted to its source below."
publisher: "Vermont Radon, an independent guide, not affiliated with the Vermont Department of Health or EPA. Not medical advice."
---

# Radon glossary

The words you’ll see on test reports, contractor quotes and official fact sheets, in plain language. Each definition links to its source and to the guide that explains more.

- **Action level**: The radon level at which the Health Department and EPA recommend reducing radon in your home: 4.0 pCi/L. They also encourage action to get below 2.0 pCi/L.[^1] [More](https://vermontradon.com/understanding-results/)
- **Active soil depressurization (ASD)**: The usual radon fix: a vent pipe and a fan that draw radon from under the house. The Health Department estimates $1,500 to $2,500 installed.[^2][^3] [More](https://vermontradon.com/fixing-radon/)
- **Aeration**: A radon in water treatment: a fan mixes your water with air inside a tank or well casing, then vents the air and radon outdoors. Estimated at around $7,000.[^3] [More](https://vermontradon.com/well-water/)
- **Advisory level (water)**: Vermont’s advisory level for radon in drinking water is 4,000 pCi/L. At or above it, the Health Department says to take action to reduce radon in your home.[^4] [More](https://vermontradon.com/well-water/)
- **Bq/m³ (becquerels per cubic meter)**: The unit many other countries and some monitors use. 37 Bq/m³ is equal to 1 pCi/L.[^5] [More](https://vermontradon.com/radon-units-pci-l-bq-m3/)
- **Closed-house conditions**: For a short-term test, close your windows and outside doors and keep them closed as much as possible during the test; for a 2- or 3-day test, close them at least 12 hours before you begin.[^6] [More](https://vermontradon.com/when-to-test-radon-vermont/)
- **Consumer digital radon monitor**: A home device that measures radon continuously while it has power. CRCPD says to verify its results with an approved test and never to use one in a real estate transaction.[^7][^8] [More](https://vermontradon.com/are-radon-monitors-accurate/)
- **Granular activated carbon (GAC)**: A charcoal filter that removes radon from water. The Health Department discourages GAC for radon because radon collected on the filter can pose a radiological hazard.[^3] [More](https://vermontradon.com/well-water/)
- **HRV or ERV (heat or energy recovery ventilator)**: Exhausts air from the home and replaces it with fresh outdoor air. Best for moderate radon levels or to supplement an ASD system; around $7,000 when no additional ducting or electrical work is needed.[^3] [More](https://vermontradon.com/fixing-radon/)
- **Long-term test**: A test left in place for 3 to 12 months, ideally including a heating season: the Health Department’s recommended way to learn your home’s typical level. The Lab’s kit is $25.[^1][^9] [More](https://vermontradon.com/how-to-test/)
- **NRPP and NRSB**: The National Radon Proficiency Program and the National Radon Safety Board: the two national directories of certified radon professionals the Health Department points to.[^1] [More](https://vermontradon.com/find-a-contractor/)
- **pCi/L (picocuries per liter)**: The unit for radon in air in the United States: picocuries per liter of air.[^6] [More](https://vermontradon.com/radon-units-pci-l-bq-m3/)
- **Radon-resistant new construction**: Building features that keep radon out: a gas-permeable layer under the slab, plastic sheeting, sealed floor openings, a vent pipe and an electrical junction box. The Health Department puts the cost at $250 to $750.[^10] [More](https://vermontradon.com/radon-resistant-new-construction-vermont/)
- **Short-term test**: A quick test for a real estate transaction or other times you need an answer fast. The Health Department says to use two short-term kits placed side by side.[^1][^11] [More](https://vermontradon.com/how-to-test/)
- **Working Level (WL)**: A unit some professional reports use. The EPA recommends fixing your home if the result is 0.016 WL or higher.[^12] [More](https://vermontradon.com/radon-units-pci-l-bq-m3/)

## Next steps

- [How to test your home](https://vermontradon.com/how-to-test/)
- [Understanding your results](https://vermontradon.com/understanding-results/)
- [How mitigation works](https://vermontradon.com/fixing-radon/)

## Sources

[^1]: **Vermont Department of Health**. [Radon in Your Home](https://www.healthvermont.gov/environment/healthy-homes/radon). Checked 2026-10-17.
[^2]: **U.S. Environmental Protection Agency**. [Consumer’s Guide to Radon Reduction: How to Fix Your Home (EPA 402/K-10/005, 2025)](https://www.epa.gov/sites/default/files/2016-12/documents/2016_consumers_guide_to_radon_reduction.pdf). Checked 2026-10-17.
[^3]: **Vermont Department of Health**. [Fixing Radon in Your Home (fact sheet, January 2024)](https://www.healthvermont.gov/sites/default/files/document/env-hh-radon-fixing-radon-in-your-home.pdf). Checked 2026-10-17.
[^4]: **Vermont Department of Health**. [Radon in Drinking Water](https://www.healthvermont.gov/environment/drinking-water/radon-drinking-water). Checked 2026-10-17.
[^5]: **Health Canada**. [Guide for radon measurements in homes](https://www.canada.ca/en/health-canada/services/publications/health-risks-safety/guide-radon-measurements-residential-dwellings.html). Checked 2026-10-17.
[^6]: **U.S. Environmental Protection Agency**. [A Citizen’s Guide to Radon (EPA 402/K-12/002, 2025)](https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf). Checked 2026-10-17.
[^7]: **U.S. Environmental Protection Agency**. [Home Buyer’s and Seller’s Guide to Radon (EPA 402/K-24/001, March 2024)](https://www.epa.gov/sites/default/files/2015-05/documents/hmbuygud.pdf). Checked 2026-10-17.
[^8]: **Conference of Radiation Control Program Directors (CRCPD)**. [Advisory: Radon Testing with Consumer Digital Radon Monitors (CRCPD Publication 25-4)](https://crcpd.org/wp-content/uploads/2025/10/25-4-Radon-Testing-with-CDRMs.pdf). Checked 2026-10-17.
[^9]: **Vermont Department of Health Laboratory**. [Radon Test Kits (Health Department Lab webstore)](https://vdh.webapps.aidcvt.com/water_supplies/radon). Checked 2026-10-17.
[^10]: **Vermont Department of Health**. [Building Radon Resistant (fact sheet, June 2025)](https://www.healthvermont.gov/sites/default/files/document/env-hh-radon-building-radon-resistant.pdf). Checked 2026-10-17.
[^11]: **Vermont Department of Health**. [Testing for Radon in Your Home (fact sheet, July 2025)](https://www.healthvermont.gov/sites/default/files/document/env-hh-radon-testing-for-radon-in-your-home.pdf). Checked 2026-10-17.
[^12]: **U.S. Environmental Protection Agency**. [Explain Working Levels (WL) and Picocuries Per Liter of Air (pCi/L)](https://www.epa.gov/radon/explain-working-levels-wl-and-picocuries-liter-air-pcil). Checked 2026-10-17.